China has 1.3 billion people, accounting for 20% of the world's population. Even a slight increase in the infection rate of human immunodeficiency virus type 1 (HIV-1) would result in a substantial increase in the absolute number of infected persons. While it is clear from seroprevalence data that HIV is spreading from high risk groups to the general population, Chinese health authorities have no effective measures for HIV incidence. HIV prevalence provides a good picture of the history of the epidemic, but does not highlight recent trends or "hotspots". HIV incidence surveillance (HIS) is needed to distinguish between recent and long-term HIV infection, to determinate patterns of infection in high-risk populations, to facilitate time-sensitive evaluation of HIV transmission dynamics, to pinpoint outbreaks, and to measure the effectiveness of prevention programs. The objective of our proposed study is to validate a novel serologic method--- an immunoglobulin G (IgG)- capture types B, E, and D ("BED")-enzyme immunoassay (BED-CEIA) to identify recent HIV-1 seroconversion --- to measure HIV incidence in China. We will assess the validity and feasibility of developing a serology based HIS to provide more accurate information for public health intervention, resource distribution, and program evaluation. The Specific Aims of This Project are: 1). To assess the validity of the BED -CEIA for measuring HIV-1 incidence by studying well-characterized pre- and post-seroconversion specimens from Chinese participants in prospective cohorts. Year one of this R03 award is in the service of Specific Aim 1. 2). Either (OPTION 1) to begin the process of developing a China-specific BED-CEIA, or (OPTION 2) to plan a pilot HIS project using the validated BED-CEIA. Whether we pursue option 1 or 2 will depend upon the results of Specific Aim 1. Year two of this R03 award will be in the pursuit of option 1 or 2, as the science dictates. [unreadable] [unreadable] [unreadable]